MRI imaging of the shoulder has been done before, generally by manual manipulation. Because the shoulder is such a complex joint, static MRI images do not provide sufficient information, especially as to shoulder instability and impingement. One of the difficulties in manipulating the shoulder is the complexity of the joint itself, and the fact that it has many different types of movement, such as abduction/adduction (FIG. 5A); internal/external rotation (FIG. 5B), and flexion/extension movement (FIG. 5C). These movements may be defined as follows:
______________________________________ abduction/adduction: swing humerus up and down (up and down relative to person standing up) abduction - start with humerus pointing towards inferior of torso and swing upwards towards head (towards superior) adduction - start with humerus at abducted position and swing down to inferior of torso internal/external rotate along axis of rotation: humerus clockwise and counter-clockwise flexion/extension: swing humerus in plane orthogonal to torso flexion - swing humerus towards front (anterior of torso) extension - swing humerus towards back (posterior) of torso. ______________________________________
During the MRI examination which may take some extensive period of time due to the necessity of acquiring several "slices" of the shoulder, the patient when inside of the aperture of the MRI apparatus must be made as comfortable as possible. At the same time, a positioning device is useful to allow for ease of incremental movement of the shoulder and to discriminate between types of movement as outlined above. The shoulder, of course, should be maintained in substantially the same physical location during the acquisition of the several images so that an effective cinematic video tape can be produced; in other words, the shoulder should be held and not necessarily restrained in a comfortable and repeatable position. In prior positioning techniques, even in the case of X-rays, manual manipulation was used.